Mich. Comp. Laws § 500.3414
An insurer shall include in a disability insurance policy, other than a health insurance policy, a provision as follows:
PROOFS OF LOSS: Written proof of loss must be furnished to the insurer at its designated office. Proof of loss for a claim for loss for which this policy provides any periodic payment that is contingent upon continuing loss must be furnished within 90 days after the termination of the period for which the insurer is liable. Proof of loss for a claim for any other loss must be furnished within 90 days after the date of the loss. Failure to furnish the proof within the time required under this provision does not invalidate or reduce the claim if it was not reasonably possible to give proof within the time required if the proof is furnished as soon as reasonably possible and, unless the claimant is legally incapacitated, not later than 1 year after the time proof is otherwise required.
MCL 500.3414